Television viewers first met secret agent CALLAN in a one-off armchair theatre play A Magnum For Schneider, in which the disgraced former top secret service agent is seconded to a government section devoted to the elimination of undesirables – by whatever means necessary.

CALLAN'S was a violent, bleak world where if you didn’t kill first, they killed you. He was a cold-blooded killer, an outsider – isolated, often in direct conflict with his superior Hunter, a codename given to all Heads of Section.

So successful was the hit-man with viewers that author James Mitchell was asked to write a series that went on to become one of the most successful programs in British TV history running from 1967 to 1972.

CALLAN made stars of the two central performers, Edward Woodward who played the disaffected agent David Callan, and Russell Hunter, as the snivelling, smelly, petty thief Lonely, the spy’s accomplice. Anthony Valentine played Callan's offsider, Toby Meres.

Callan has retired from the Department, runs his own military memorabilia shop called 'The Old Brigade' and is living with a woman called Margaret. Lonely has also moved on. He has a successful plumbing business and is engaged to be married.

But you are never retired when you work for The Department, and when Callan hears from the new Hunter that his services are required he discovers that a man named Hagggerty is writing a tell-all book which names Callan as a professional killer. Hunter tells Callan that it is a non-Departmental matter, and that it is between Callan and Haggarty. Callan enlists Lonely's aid, gets his magnum pistol out of storage at the bank and prepares to kill once again.